With the widespread deployment of user consumer devices that are interconnected via Internet access gateways, equipped with wired and wireless network interfaces, one can currently speak of home networks. Most devices and appliances in the home network use the home network to communicate with the outside world, via the Internet. The home appliances are connected to equipment commonly referred to as a home gateway. The home gateway is an ‘always on’ device that not only ensures Internet connection for the home network devices, but also, for example, connectivity for a set of telephone devices for telephony over IP. Often, the home gateway is connected to the Internet via a single ADSL (Asymmetrical Digital Subscriber Line) connection. All devices in the home share thus the same ADSL connection via the gateway device. The ADSL connection offers an asymmetrical bandwidth in terms of upload and download bit rate. Bandwidth available for upload is some factors lower than bandwidth available for download. This asymmetrical bandwidth is generally convenient for the use of the home network devices that tend to have a more important need for download bandwidth than for upload bandwidth.
In the same time, data stored by the home devices tends to increase in volume: photos, movies, documents. Users of the home network feel the need to protect their data. Local backup on a mass storage device is unsatisfying because the data is not secured against accidental failure, theft or fire. Transferring voluminous data to an external storage on the Internet is time-consuming because of the low upload bit rate that additionally needs to be shared with other home network devices. If a full data backup takes several days to upload to the external storage over an ADSL connection, any data loss that occurs in the home network to data that was modified after the full data backup was started and before a next full data backup has been completed is lost, the modified data not being secured against data loss until it in turn is completely transferred as part of a next full backup.
There is thus a need for an improved data transfer method, so that data stored is better secured against data loss, taking into account the bit rate of the upload link, and covering ‘intermediate’ transfers.